sextet vs half a dozen

sextet and half a dozen both are nouns.

Word	Noun	Adjective	Verb	Adverb
sextet	Yes	No	No	No
half a dozen	Yes	No	No	No

As nouns, sextet and half a dozen are synonyms defined as:

sextet and half a dozen: the cardinal number that is the sum of five and one

Other synonyms of sextet include 6, Captain Hicks, hexad, sestet, sextuplet, sise, six, sixer, VI.

sextet (noun)	half a dozen (noun)
a musical composition written for six performers	the cardinal number that is the sum of five and one
six people considered as a unit
a set of six similar things considered as a unit
six performers or singers who perform together
the cardinal number that is the sum of five and one